The prior art for measuring the meter-range distance to an article outdoors or indoors using a laser beam includes the following measurement methods.
1) Method using an optical radar range finder PA1 2) Active stereo method PA1 3) Stereo vision PA1 a lens array including a plurality of lenses having identical lens characteristics and disposed at uniform intervals on a plane, the lens array having a hole formed within the plane for allowing passage of the laser beam projected from the laser oscillator; PA1 a photodetector array including a plurality of photodetectors disposed on a plane and corresponding to each lens constituting the lens array, the photodetectors in the photodetector array being disposed at a distance of a focal length of the lens from the lenses in the lens array, the photodetector array having a hole formed within the plane for allowing passage of the laser beam projected from the laser oscillator; PA1 the laser oscillator projecting the laser beam toward the article in such a manner that a direction of the laser beam becomes perpendicular to the photodetector array and the lens array and that the laser beam passes through each of the holes formed in the photodetector array and the lens array; PA1 the lens array, the photodetector array, and the laser oscillator being disposed in front of the article so as to be separated from the article in that order; and PA1 calculating means for calculating an effective area on the photodetector array on the basis of an output of each photodetector in the photodetector array, when the laser beam reflected from the article is sensed by the photodetector array via the lens array, and for calculating a distance from the lens array to the article on the basis of the effective area and an angle of view of the lenses constituting the lens array. PA1 an imaging lens array including a plurality of lenses disposed on a plane; PA1 an imaging photodetector array including photodetectors disposed on a plane and having prescribed resolutions corresponding to each lens constituting the imaging lens array, the photodetectors in the photodetector array being disposed at a distance of a focal length of the lens from the corresponding lenses in the lens array; PA1 a reproducing lens array including a plurality of lenses disposed on a plane and having lens characteristics identical to lenses constituting the imaging lens array; PA1 a reproducing emitter array including emitters disposed on a plane and corresponding to each lens constituting the reproducing lens array and having the same size as the photodetectors constituting the imaging photodetector array, the emitters of the emitter array being disposed at a distance of a focal length of the lens from corresponding lenses in the reproducing lens array; PA1 a reproducing sensor array including a plurality of photodetectors disposed on a plane, for sensing light passing through the reproducing lens array; PA1 the imaging lens array, the imaging photodetector array, the reproducing emitter array, the reproducing lens array, and the reproducing sensor array being disposed in front of the article so as to be separated from the article in that order; PA1 transferring means for transferring an output of each photodetector in the imaging photodetector array to each corresponding emitter in the reproducing emitter array and causing emission by the emitters, when the light reflected by the article passes through the imaging lens array and is sensed with the imaging photodetector array; PA1 moving means for moving the reproducing sensor array in a direction of distance measurement for the article, when the light emitted by the reproducing emitter array passes through the reproducing lens array and is sensed with each photodetector of the reproducing sensor array; and PA1 calculating means for calculating a distribution of an intensity of light sensed with each photodetector of the reproducing sensor array for each position to which the reproducing sensor array is moved and for calculating a distance to the article from the imaging lens array and a shape of the article on the basis of the light intensity distribution for each position. PA1 an imaging lens array including a plurality of lenses disposed on a plane; PA1 an imaging sensor array including photodetectors disposed on a plane and having a prescribed resolution and corresponding to each of the lenses constituting the imaging lens array, the photodetectors of the photodetector array being disposed at a distance of a focal length of each lens from corresponding lenses of the imaging lens array; and PA1 calculating means for calculating pixels of an imaged image of the photodetectors corresponding to a coordinate position of each element in space on the basis of a positional relationship between the lenses in the imaging lens array and the photodetectors in the imaging photodetector array, for determining coordinate positions representing a profile of the article from among the coordinate positions in the space by comparing image information of the pixels found, and for finding a distance to and a shape of the article on the basis of the coordinate positions determined. PA1 the calculating means finds pixels in the imaged image corresponding to coordinate positions of each element of the space divided with the first means for dividing, determines coordinate positions representing a profile of the article from among each of the coordinate positions in the space by comparing the image information of the pixels determined, and finds a distance to and a shape of the article on the basis of the determined coordinate positions; PA1 determining means for determining whether the article is present in which area of the space on the basis of results of calculations in progress by the calculating means; PA1 second dividing means for dividing into a further plurality of elements those elements divided by the first dividing means, for an area, in which the article is present, of the space where it is determined that the article is present; and in which PA1 the calculating means finds pixels in the imaged image corresponding to coordinate positions of each element of the area where the article is present and which is divided by the second dividing means, determines coordinate positions representing a profile of the article from among each of the coordinate positions of the area where the article is present by comparing the image information of the pixels found, and finds the distance to and the shape of the article on the basis of the coordinate positions determined. PA1 plurality of modules are selected from among the two or more modules, so that a distance to one module or between two modules farthest apart becomes less than or equal to the prescribed distance between modules, when a distance from the module to the article is less than or equal to a prescribed distance between module and article; PA1 plurality of modules are selected from among the two or more modules, so that a distance between the two modules farthest apart becomes greater than the prescribed distance between modules, when the distance from the modules to the article is greater than the prescribed distance between module and article; and PA1 a distance to and a shape of the article are measured by using the cameras installed in the selected modules.
The method using an optical radar range finder is a distance measuring method of beaming a laser beam to an article and measuring the time until that reflected light returns; the advantage of this method is that it can rapidly measure distant articles.
On the other hand, the active stereo method is a distance measuring method of beaming a laser beam to an article with a laser apparatus, imaging that with a camera, and measuring the distance by triangulation; the advantage of this method is that it can realize distance measurement with a simple apparatus. Also, the prior art for measuring meter-range distance to an article which is outdoors or indoors includes the following measuring method.
This stereo vision method finds corresponding points in two image data and measures distance through triangulation; the advantage of this method is that it can realize distance measurement with a simple apparatus.
The method with an optical radar range finder may only measure the time for the reflected light to return, but the measurement apparatus is large and complex; it also requires precise calibration.
On the other hand, the active stereo method can effect distance measurement with an apparatus having a comparatively simple constitution; however, precision is required in the positional relationship of the camera and laser apparatus and the measurement of angle of view of the laser. In effect it requires precise calibration. Also, the laser apparatus and camera must be separated by a large distance because it is necessary to perform triangulation. Out of necessity, the entire apparatus becomes large.
In this way, the distance measuring apparatus relating to the prior art requires precise calibration of the apparatus; therefore a problem is that the precision of distance measurement itself decreases when precise calibration cannot be carried out. Another problem is that the space occupied becomes large because the apparatus as a whole becomes large in size.
Therefore it is a first object of the present invention to provide a distance measuring apparatus wherein problems such as requiring much space are avoided through the reduction of the overall size of the apparatus, which is able to effect distance measurement precisely, even without sufficient calibration.
The aforementioned method using an optical radar range finder has the advantage of being able to measure long distances rapidly; however this method is unable to effect distance measurement accurately in an environment where the light is absorbed and scattered in the propagation path of the laser beam or when the laser beam is entirely reflected by the surface of the article.
Also, this method essentially effects point measurement, measuring the distance to one point of the article. For this reason it requires a mechanism to scan the laser beam for measuring the shape of a large article or measuring a wide range on an article. In this case, the scanning requires more time and the apparatus as a whole becomes more complex because of the added scanning mechanism.
On the other hand, the method using stereo vision can effect distance measurement with a comparatively simple apparatus; however, it is very difficult to match screens for triangulation. Of course a match is not necessary when the subject article is one point, but that is an unusual case. Matching is impossible for a complex article and the calculation time necessary for matching becomes very long.
In this way, the conventional distance measuring apparatus basically measures the distance to one point; measuring the distance to the surface of a complex object results in the following problems: the apparatus becomes complex and the time for scanning the laser beam and calculations for distance measurement becomes very long.
It is a second object of the present invention to enable a distance measurement with an apparatus having a simple constitution and enable to complete the measurement in a short period of time without requiring time for calculations, etc., even when measuring the distance to the surface of a complex article.
Technology to measure the distance to an article from the results of imaging the article with a plurality of cameras has been noted in Japanese Patent Laid-open Publication No. 61-66107 and Japanese Patent Laid-Open Publication No. 6-241749.
This technology is explained with reference to FIG. 19; distance measurement is carried out with roughly the following procedures.
(1) Prepare three cameras 301, 302, 303, sample characteristic point in an image 304 from the camera 301 which is the reference camera from among those cameras, find the reverse projection 309.
(2) Project the reverse projection 309 on the images 305, 306 from each camera 302, 303 and find candidate corresponding points on those projections 309a, 309b.
(3) Find the reference reverse projections 310 . . . (represented with dotted line) for all candidate corresponding points and find the intersections of these reference reverse projections 310 . . . with the reverse projection 309. From the results, establish the coordinate position of the intersection 308, having many crossings, as the coordinate position of the characteristic point on the article 307.
(4) Execute the aforementioned processing (1)-(3) for all characteristic points on the reference image 304, find the coordinate positions of all candidate points on the article 307, and find the shape of the article 307.
In this way, this technology requires the execution of the complex processing shown in (1)-(3) in sampling a characteristic point on the reference image 304. Moreover, it is necessary to sample and carry out complex processing for all characteristic points on the reference image 304.
For this reason, the calculation time becomes long and this method cannot be used for real time measurement.
Also, camera lens distortion and quantum errors, etc., sometimes result in the intersection 308 of the reverse projection 309 with reference reverse projection 310 not existing. In such a case, the position where each reference reverse projection 310 . . . is closest to the reverse projection 309 must be corrected as the intersection 308. The operation for such a correction greatly lengthens the calculation time.
A paper relating to this technology is "Method for resolving multiple scale, three-dimensional structures by voting from multiple viewpoints using .DELTA.2G filtering" (Journal of the Institute of Electronics, Information and Communications Engineers, D-II, Vol. J78-D-II, No. 3, March 1995).
In the technology described in this paper, space is divided among box cells (boxes) and voting effected in box cells where intersections are present. In this case, the precision of the measurement is adjusted by initially making the divisions into box cells rough and then making the divisions smaller for the box cells having much voting.
However, this technology does not reduce the amount of calculations for calculating intersections, even with rough box cells, and does not shorten the calculation time.
Also, a risk is that, when the number of divisions is increased and detailed measurement carried out for box cells with many intersections, the number of votes for the intersections decreases and the precision of measurement worsens instead.
In this way, the conventional technology, for measuring the distance to and shape of an article from images from a plurality of cameras, has increased calculation time and may not be usable in real time measurement.
Therefore, it is a third object of the third invention of the present invention to constitute the apparatus so as to complete real time measurement and effect calculations in a short period of time, when finding through calculations the distance to and shape of an article from images from a plurality of cameras, with the space to be measured divided into each of the elements.
As discussed above, with the application of the third invention of the present invention to find through calculations the distance to and shape of an article from images from a plurality of cameras, with the space to be measured divided into each of the elements, there may be errors in measurement resulting from the article subject to measurement. That article may be an item with little difference among portions of its surface or with surface characteristics that are difficult to capture: an item with little or no pattern on its surface, or an item with many similar patterns, etc.
It is an object of the fourth invention of the present invention to constitute the apparatus so as to be able to measure the distance to an shape of an article, even an article with surface characteristics that are difficult to capture, precisely and accurately.
As discussed above, with the application of the third invention of the present invention to find through calculations the distance to and shape of an article from images from a plurality of cameras, with the space to be measured divided into each of the elements, a risk is that there may be increases to the operation time and decreased efficiency of measurement with the uniform division of space.
Therefore it is a fifth object of the present invention to improve the efficiency of measurement by changing the number of divisions per uniform area of space to be measured according to the article and circumstances of measurement.
For the aforementioned fourth invention of the present invention, it Is a sixth object to complement the measuring apparatus of the aforementioned fourth invention of the present invention with the addition of a measuring apparatus which can measure portions of an article that are difficult to measure, so as to enable the apparatus to effect measurement of the entire surface of the article.
Also, because of the distance to an article from the measuring apparatus according to the aforementioned third invention, the precision of measurement drops in relation to the distance between a plurality of cameras.
Therefore, it is a seventh object of the present invention to constitute the apparatus so as to be able to sustain the precision of measurement at a prescribed level or better regardless of the distance from the measuring apparatus to the article.